1. Field of the Invention
This invention relates to a method for spraying an anti-termite agent and the apparatus therefor for the termite-proofing of a house.
2. Description of the Prior Art
For termite-proofing underfloor portions, etc. of a house, an anti-termite agent is usually sprayed by means of a spraying apparatus, for example, an engine- or motor-powered spraying machine in which the agent is transported in liquid form under pressure and to which are connected a hose and a spray gun through which the liquid agent is sprayed. The front end portion (nozzle) of the spray gun used for this purpose is an important element which determines the condition of agent spray. Spray guns are commercially available in various forms according to various uses.
Hitherto, for termite-proofing purposes, a pistol type spray gun (hereinafter referred to as spray gun) 1 has been most commonly used, which is typically has the structure shown in FIG. 1. This spray gun 1 is described with reference to FIG. 1. A handle portion 2 of the spray gun 1 has an agent supply pipeline 3 provided therein which communicates with a conduit 5 provided in a barrel portion 4 formed integrally with the handle portion 2. The conduit 5 communicates with a valve chamber 7 in a mechanism portion 6 fixed to the barrel portion 4.
An external thread 9 is cut on a portion adjacent the front end of a tubular body 8 which defines the valve chamber 7. At the front end of the tubular body 8 there are disposed a valve member 11 having a valve seat 10, and a tapered nozzle 12 having the shape of a generally truncated cone, which are fixed in the foregoing order to the tubular body 8 by means of a cap 13 screwed into threaded engagement with the external thread 9.
The tubular body 8 is formed at its base end side with an insertion hole 15 through which a valve rod 14 is inserted. At the interior side of the insertion hole 15, the valve rod 14 has a locking protrusion 16 formed thereon and the tubular structure 8 has a recessed portion 17 which is diametrically smaller than the inner diameter of the tubular body 8 and larger than the insertion hole 15.
At its front end the valve rod 14 has a tapered valve body 18 formed thereon which is engageable with the valve seat 10 of the valve member 11. The valve rod 14, at its base end side, is adapted to be back and forth movably fitted in a guide hole 19 bored in the handle portion 2 so that the valve rod 14 can be guided free of jolting while being movably supported at a point adjacent the insertion hole 15. A control lever 20 is pivotally supported at its one end on a pivot shaft 21 in the barrel portion 4 so that it is angularly displaceable about the pivot shaft 21. Such a control lever 20 is angularly displaceably connected with the valve rod 14, both the lever 20 and the rod 14 being biased by a coil spring 22 in the direction of valve closing (i.e., in the leftward direction in FIG. 1).
A chemical agent transported under pressure through the agent supply pipeline 3 is fed into the valve chamber 7 via the conduit 5. In this case, unless the control lever 20 is manipulated for movement in the direction of arrow A1, the valve body 18 remains in contact with the valve seat 10 by the spring force exerted by the coil spring 22, the chemical agent being thus prevented from jetting from the nozzle 12.
To spray the agent, the control lever 20 is manipulated against the biasing force of the coil spring 22 and in the direction of arrow A1, whereby the valve body 18 is moved away from the valve seat 10 so that the agent is allowed to jet out from the nozzle 12. The nozzle 12 used in the spray gun is simply of such a construction that the area of its front end is reduced so as to allow vigorous jetting of the agent.
The conventional spraying apparatus employs a nozzle 12 having such a small jet orifice 23 for simply spraying the agent in a rod-like or mist-like pattern; therefore it has a drawback in that during a spraying operation, there may be considerably amount of splash back of liquid from the objects being treated (such as house walls and pillars) and, if the liquid is sprayed in a mist-like pattern, there is considerable fly-off of fine misty particles of the liquid which will contaminate the operator. In order to ensure a sufficient discharge and a sufficient range of the spray, there is required a pressure of 25-30 kg/cm.sup.2 (pressure at the operator side); however, operation under such pressure will involve a greater possibility of fly-off of liquid mist, which naturally means a greater possibility of the operator being contaminated. If the pressure is reduced to 5-10 kg/cm.sup.2 in order to reduce the possibility of such fly-off, there is a reduction in the rate of liquid discharge, though such fly-off can be reduced. This naturally means longer operation item, and after all it is not helpful for the purpose of the operator's safety.